Display discharge tube having improved display substrate and method of making same

ABSTRACT

A display substrate includes a display plate having mutually separated, integral projecting symbol segments formed thereon by a press-forming technique. A metallic layer is provided on the raised surfaces of the segments to form the luminous cathodes representing the symbol segments. Electrical connection of the metallic layers to an energizing source is made by means of pins extending through the segments and the plate, the upper surfaces of the pins being in the same plane as the raised surface of its respective segment.

United States Patent 1 72] Inventors Miehio Koehhnh;

Shloetsu Soto, both of Tokyonl ll l [21 AppL No. 13,302 [22] Filed Feb. 24, 1970 [45] Patented AI. I0, 1971 [73] Assignee Japan Radio Company, Limited T ky J II [54] DISPLAY DISCHARGE TUBE HAVING IMPROVED DISPLAY SUBSTRATE AND METHOD OF MAKING SAME QChIIgSDroWllgflp.

[52] 0.8.0. 313/1096, 313/210,313I217 (51] InLCl. h llflljl/JO, HOlj 1/52 [50] FteldolSeu-eh 313/1095,

[S6] llelerenoes Cited UNITED STATES PATENTS 2,833,949 5/1958 Driscoll 313/217 3,260,881 7/1966 Kuchinsky 313/1095 3,302,052 1/1967 Schwab 313/1095 Primary Examiner Ronald L. Wibert Assistant Examiner-J Rothenberg Anomey- Flynn & Frishauf ABSTRACT: A display substrate includes a display plate having mutually separated, integral projecting symbol segments formed thereon by a press-forming technique. A metallic layer is provided on the raised surfaces of the segments to form the luminous cathodes representing the symbol segments. Electrical connection of the metallic layers to an energizing source is made by means of pins extending through the segments and the plate. the upper surfaces of the pins being in the same plane as the raised surface of its respective segment.

PATENTEDAucmBn 0,588.02]

MICHIO KOSHIZUKA SHINETSU SATO INVENTORS WMJZW ATTOR N EYS DISPLAY DISCHARGE TUBE HAVING IMPROVED DISPLAY SUBSTRATE AND METHOD OF MAKING SAME The present invention relates to improvements in display discharge tubes which display alpha-numeric symbols or other symbols in a mosaic manner.

In known display discharge tubes, which provide a display of the type generally termed "mosaic display," a mica plate having a number of small holes or openings therein is used for the display substrate. In the known tubes, the cathodes are comprised of thin, elongated, stainless steel plates having tabs extending therefrom, the tabs being inserted into the small holes or openings and then being bent to fixedly secure the cathodes to the mica plate in a desired configuration. The cathodes form segments of the symbols to be displayed. This type of display discharge tube has the disadvantage that in the manufacture of the display plate, a large number of manufacturing steps must be performed and that the quality of the resulting finished products is highly nonuniform. These disadvantages are due mainly to the fact that the cathode segments corresponding to the symbol segments are very small in size and are formed by hand working from the pieces of stainless steel. Further, the hand worked symbol segments are mounted on the mica display substrate piece by piece. This procedure obviously leads to variations in the characteristics of the resulting finished products and increases the cost of the resulting products.

The main object of the present invention is to effectively obviate the above disadvantages of the prior art tubes and to provide a display discharge tube having a display substrate which can be more easily mass produced and wherein the resulting finished product has highly uniform characteristics.

SUMMARY OF THE INVENTION According to the present invention, a display substrate for a display discharge tube comprises a display plate having at least predetermined symbol segments projecting therefrom, the projections being integral with the display plate and mutually separated. The display plate is preferably made of ceramic material. Funher included is a metallic coating on the surfaces of the symbol segments which are to be displayed.

The method of fabricating the display substrate for a display gas discharge tube according to the present invention includes press forming a display plate to form a plurality of integral projecting portions thereon, the projecting portions being mutually separated and corresponding to at least predetermined symbol segments. Lead pin holes, which preferably extend in a funnel shape towards the raised surfaces of the projections, are formed in the display plate to accept lead pins having a mating configuration. Then, a metallic layer is applied to the raised display surface of the projections, the metallic layers on the projections serving as the cathode electrodes of the tube.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front, partially cutaway view of a display discharge tube according to the present invention.

FIGS. 2(a) and 2(b) are front and side views, respectively, showing in an enlarged scale the display substrate in the display discharge tube of FIG. I;

FIG. 3 is a transverse cross-sectional view of the display substrate taken along a line A-A' in FIG. 2(a); and

FIG. 4 is a disassembled view, in enlarged scale, of a portion of the display substrate shown in FIG. 3.

In the drawings, the same reference numerals are used to designate identical parts throughout.

Referring now to the drawings, a display tube of the present invention includes an envelope 1, within which is mounted a sandwich-shaped stem portion which includes steatite insulators 2 and 3 with a glass tablet 4 pinched therebetween. Lead wires 5 extend from the base of envelope 1 and within the envelope l is provided, a mercury giver/getter container 6, all as well known in the art. A mica plate 7 supports a display substrate 8 and a mesh-shaped anode structure 9 (the mesh por' tion 9 being shown in FIG. I encircled by a dotted line). The display plate 14 of display substrate 8 is preferably formed from ceramic material. Symbol segments 10 and II project from the surface of the display plate 14 and have a trapezoidal cross section with respect to the surface of display plate 14 from which the symbol segments project (see FIGS. 3 and 4). Segment 1] corresponds to a decimal point display and segments 10 are segments of numeric displays in the illustrated embodiment. Segments l0 and 11 have a metallic coating 15 thereon (see FIGS. 2-4) which acts as the luminous cathode electrodes for the tube. Segments l0 and II are integral with the display plate 14.

Referring to FIGS. 2, 3 and 4, lead pin holes 12 having funnel-shaped portions are provided in the display substrate 8 through die trapezoidal projections 10 and 11. The funnel shaped portions 120 open towards the raised (or luminous display) surface of the projections. Conducting pins 13 are provided which have funnel-shaped upper portions 134 which mate with respective funnel-shaped portions 12a of holes 12. A lead pin 13 is inserted into a lead pin hole 12 from the upper (or display) side of plate 14 (see FIGS. 3 and 4). When the lead pin I3 is pulled out from its lower end after insertion, the funnel-shaped top portions of the lead pin and lead pin hole will make intimate contact with each other, and the top plane of the lead pin will lie in the same horizontal plane as the upper or luminous display surface of the projecting segments 10 and II. The stem portions 13b of lead pins I3 are dimensioned to form a press-fit in the stern portions 12b of holes I2. After the lead pins I3 have been inserted in the holes 12, a metallic coating serving as a luminous cathode is applied onto the raised (or display) surfaces of the segments remote from the display plate I4 and onto the upper surface of the pins 13 utilizing a method described below. After assembly of the dis play substrate 8, the pins 13 are connected to lead wires 5, in a manner known in the art to make external connections for selectively energizing the symbol segments of the tube. The operation of such a display tube is well known in the art.

When a lead pin 13 is inserted into a lead pin hole 12, the funnel-shaped top portions thereof make intimate contact with each other, the top plane of the lead pin 13 being in the same horizontal plane as the upper surface of the segments. This is achieved in one operation, thereby facilitating assembly. By virtue of the above-described structure, the lead pin 13 is rigidly and fixedly secured to the display plate I4 in a mechanical manner due to the tension provided by the pressfit between the stem 13b of the pin and the portion 12b of the hole. Thus, the pin will not disengage from the lead pin hole, and the upper surfaces of the pin I3 and the projecting segments will remain in the same plane.

Due to the large area of the contact surface of the lead pin 13 (i.e., the upper surface of the funnel-shaped portion of the pin), the electric contact resistance between the pin and the metallic coating is reduced.

The operation of mounting the pins I3 to the cathodes is very simple, further lending fabrication of the present display substrate to mass production.

As the material for the display plate 14, ceramic is preferably employed. Even if spattering due to glow discharge during operation of the tube should occur, since the surface is very rough, the surface resistance would not be reduced for a normal degree of spattering. However, in prior art tubes, in the case of operation for a very long time or in the case of operation causing heavy spattering, this would not be true. In known tubes where the cathode segments are placed on the surface of the material of a flat display substrate without being projected therefrom as in the present invention, the adverse effects of spattering cannot be eliminated. In these known tubes, as spattering due to the operation of the display tube proceeds, the cathode glow extends to the peripheral edge of the segment, so that it may become impossible to achieve proper operation. Since the adjacent cathode segments have short separation distances, surface leakage would soon occur therebetween and the adjacent cathode segments would become conducting with respect to each other, thereby resulting in erroneous displays.

The above adverse effects of spattering are virtually eliminated in the tube according to the present invention. by providing display segments which project from the surface of the display substrate.

By virtue of the present invention, the display substrate 8 has projecting segments wherein very narrow gaps exist between the end surfaces of the adjacent segments. However. in operation of the display discharge tube, spattering from the metallic cathode surfaces cannot reach the narrow gaps. This is due to the projecting segments which effectively extends the distance between adjacent metallic cathode surfaces while allowing narrow gaps between adjacent segments. Therefore, the insulation between the adjacent metallic cathode segments is very good. Thus, erroneous displays due to poor insulation between adjacent cathode segments, as is the case in conventional display tubes of this type, do not occur.

Also, adhesion of spattered material onto the side surfaces other than the end surfaces of the projecting cathode segments in the tube of the present invention is greatly reduced by proper selection of the gas pressure within the discharge tube, and by providing mercury therein, it is possible to suppress the spattering from the cathodes to substantially zero.

The method of making the display discharge tube of the present invention includes fabricating a display plate 14 with projecting portions 10 and ll which have substantially trapezoidal cross sections by a press-forming method. Then, lead pin holes 12 are formed through the plate 14 and through the projecting portions, the lead pin holes 12 having funnel shaped portions 120 opening towards the raised surface of the projections. Then, lead pins 13 having mating funnel-shaped portions 13a are inserted into the holes 12 with the upper surfaces of the pins lying in the same plane as the raised surfaces of the projections. The holes may be formed by drilling, etc.

Then, a metallic coating l (see FIGS. 3 and 4) is applied to the upper (or display) surfaces of the projecting segments and I1 by, for example, applying a paste essentially containing a mixture of metallic powders and glass filler onto the upper surfaces of the segments, and sintering them at about 800 C. The paste may be applied by a printing process which makes use of a mask or a screen, by an offset process in which the paste is simply held flat and pressed onto the display surfaces of the segments, or by a transfer process in which the paste is preliminarily coated on a tape or the like and is then transferred therefrom onto the segments. Other processes may be used to uniformly apply the metallic coating to the display surfaces of the segments.

As the metal for the metallic coating, nickel is Preferable since it is insoluble in mercury, and since it is not easily oxidized during the sintering process. If necessary, it is also possible to use an alloy as the metallic coating.

As mentioned above, the display plate I is preferably formed from ceramic material such as alumina, forsterite, steatite, etc. The selection of a particular material is made in accordance with the method used to apply the metallic coating onto the display surface of the projections. Generally, if the metallic coating is applied at a relatively low temperature (such as, approximately 800 C), a steatite of low cost can satisfactorily be used.

If desired, the substrate material may be colored black, for example, to make the resulting display clearer.

Summarizing, the present improved display substrate for a display discharge tube effectively eliminates erroneous displays due to spattering and thereby increases the life of the tube. Further, by virtue of forming of the substrate with projecting portions by means of a press-forming technique, to form projecting segments integral with the display plate, it is possible to form precisely shaped and accurately located segments on the display plate with only a single press-forming operation. This not only makes the improved display substrate suitable for low cost mass production, but also enables dis lay tubes to be fabricated having more uniform characteria cs.

The pin hole 12 and pin 13 configuration also facilitates assembly of the structure, thereby further enhancing mass production, and provides improved electrical and mechanical properties. In the above embodiment, the integral projecting symbol segments having a trapezoidal cross section with respect to the surface of the display plate have been used for the simplification of the explanation, however, any other shapes of the projecting segments may be employed.

We claim:

1. [n a display gas discharge tube, a display substrate comprising:

a display plate having at least one symbol segment projecting from a surface thereof, said symbol segment being integral with said display plate;

a metallic layer on the surface of said at least one projecting segment remote from said surface of said display plate from which said segment projects, said metallic layer serving as a cathode electrode for said display gas discharge tube.

2. The tube according to claim I comprising a plurality of mutually separated symbol segments projecting from said surface of said display plate, said segments being integral with said display plate; and a metallic layer on the surface of each projecting segment remote from said surface of said display plate from which said segments project, said metallic layer serving as cathode electrodes for said tube.

3. The tube according to claim I wherein at least one lead pin hole is provided in said display substrate extending through said at least one projecting segment and through said display plate, said display substrate further comprising at least one lead pin located in said at least one lead pin hole, the upper surface of said at least one lead pin extending to said remote surface of said at least one projecting segment and the upper surface of said lead pin contacting the metallic layer on said at least one projecting segment.

4. The tube according to claim 2 comprising a plurality of lead pin holes in said substrate, at least one hole extending through each segment and through said display plate, and a plurality of lead pins located in respective lead pin holes, the upper surface of said lead pins extending to the remote surfaces of respective segments and contacting the metallic layer on respective segments.

5. The tube according to claim 3 wherein the upper surface of said at least one lead pin is in the same plane as said remote surface of said at least one projecting segment.

6. A display gas discharge tube as claimed in claim 3 wherein said lead pin is press fit within at least a portion of the lead pin hole within which it is located.

7. A tube according to claim 3 wherein said at least one lead pin hole has a funnel-shaped portion opening towards said remote surface of said at least one projecting segment and wherein the upper portion of said at least one lead pin has a mating funnel-shape.

8. A display gas discharge tube as claimed in claim 7 wherein the non-funnel-shaped portion of said lead pin is press fit within at least a portion of the non-funnel-shaped portion of the lead pin hole within which it is located.

9. The tube according to claim 3 comprising a sealed tube envelope; a plurality of lead wires extending therefrom; an anode electrode; means supporting said anode electrode and said display substrate; and means electrically coupling said at least one pin to said lead wires to enable energization of said at least one cathode electrode. 

1. In a display gas discharge tube, a display substrate (8) comprising: a display plate (14) having at least one symbol segment (10, 11) projecting from a surface thereof, said symbol segment (10, 11) being integral with said display plate; and a metallic layer (15) on the surface of said at least one projecting segment remote from said surface of said display plate from which said segment projects, said metallic layer serving as a cathode electrode for said display gas discharge tube.
 2. The tube according to claim 1 comprising a plurality of mutually separated symbol segments projecting from said surface of said display plate, said segments being integral with said display plate; and a metallic layer on the surface of each projecting segment remote from said surface of said display plate from which said segments project, said metallic layer serving as cathode electrodes for said tube.
 3. The tube according to claim 1 wherein at least one lead pin hole (12) is provided in said display substrate extending through said at least one projecting segment and through said display plate, said display substrate further comprising at least one lead pin (13) located in said at least one lead pin hole (12), the upper surface of said at least one lead pin extending to said remote surface of said at least one projecting segment and the upper surface of said lead pin contacting the metallic layer on said at least one projecting segment.
 4. The tube according to claim 2 comprising a plurality of lead pin holes in said substrate, at least one hole extending through each segment and through said display plate, and a plurality of lead pins located in respective lead pin holes, the upper surFace of said lead pins extending to the remote surfaces of respective segments and contacting the metallic layer on respective segments.
 5. The tube according to claim 3 wherein the upper surface of said at least one lead pin is in the same plane as said remote surface of said at least one projecting segment.
 6. A display gas discharge tube as claimed in claim 3 wherein said lead pin is press fit within at least a portion of the lead pin hole within which it is located.
 7. A tube according to claim 3 wherein said at least one lead pin hole has a funnel-shaped portion opening towards said remote surface of said at least one projecting segment and wherein the upper portion of said at least one lead pin has a mating funnel shape.
 8. A display gas discharge tube as claimed in claim 7 wherein the nonfunnel-shaped portion of said lead pin is press fit within at least a portion of the nonfunnel-shaped portion of the lead pin hole within which it is located.
 9. The tube according to claim 3 comprising a sealed tube envelope (1); a plurality of lead wires (5) extending therefrom; an anode electrode (9); means (7) supporting said anode electrode (9) and said display substrate (8); and means electrically coupling said at least one pin (13) to said lead wires (5) to enable energization of said at least one cathode electrode. 